1. Field of the Invention
This invention relates to refrigeration systems through which a volatile refrigerant is circulated along with oil and to eductor means for causing oil to return to its compressor source without the need for providing gas-flow risers having a high internal gas velocity with its accompanying high pressure drop.
2. Discussion of Prior Art
It is common for refrigerating systems employing one or more compressors for circulating a volatile refrigerant to experience oil transfer from the compressor to the flow stream of volatile refrigerant pumped by the compressor. In larger systems it is common to design vapor flow piping with internal vapor velocities high enough to ensure entrainment of such oil so that it can be reliably carried back to its source, the compressor. It is admitted that the smaller pipes needed to generate the higher vapor velocities have a reduced first cost. However, the higher internal vapor velocities required for this purpose generate vapor pressure drops which degrade system performance and efficiency, thereby imposing higher operating costs for the life of the equipment. The performance degradation is most pronounced where the oil flow is desired to occur in `suction lines`, those pipes carrying refrigerant vapor from a cooling coil or evaporator to a compressor. The portion of systems in which suction lines or pipes or conduits reside are frequently called "low-sides", referring to the lower pressure existing in those pipes or conduits. Since any particular low-side may not be the region of lowest pressure within a given system, the term "lower pressure side" will be used interchangeably with the term lowside.
Compressors ordinarily are constructed with oil sumps or reservoirs. These are substantially always at the pressure of the suction line or conduit from which they pump. Therefore, such reservoirs or sumps are part of the low-side or lower pressure side as well as suctions lines and suction conduits.
While the use of eductors and venturis is well known for pumping waste water and slurries from one point to another, their application for oil return instead of through vertical risers in refrigeration systems is not known heretofore.
The term eductor as used herein applies to venturi-type devices having no moving parts. Eductors employ a higher pressure fluid to create an area of lower pressure into which a desired fluid at one location is attracted and conveyed to a second location.
Eductors are also known as venturis, jet-pumps, ejectors, syphons, injectors and aspirators.
They are manufactured by several companies one of which is the Fox Valve Development Corp. located at Hamilton Business Park, Unit 6A, Franklin Road, Dover N.J. 07801.